浅析碾压土石坝施工质量控制要点

土石坝施工技术因为有施工成本低、维护便利、施工工艺简单等优势,在水利水电工程施工中较为常见,且已被广泛应用。以此为背景,本文先对土石坝的相关内容进行了分析,然后阐述了碾压土石坝施工工艺与质量控制,以供参考。

Intermediaries and Targets of the Oxidative Stress Induced by Natural Sunlight in Escherichia coil

The lethal effect produced by sunlight in bacteria depends on the photodynamic action of the ultraviolet component of the radiation. Neither the reactive oxygen species involved nor the targets for damage have been certainly identified, and the aim of this study was to address these issues. During exposures to natural sunlight, photo-protection provided by nitrogen sparging was compared with which provided by the addition of L-histidine （an efficient scavenger for hydroxyl radical and singlet oxygen） or mannitol （an hydroxyl radical scavenger which reacts poorly with singlet oxygen） to the irradiation medium. Both scavengers reproduced for the most part the effect of oxygen depletion, indicating that damage depends mainly on hydroxyl radical generation. Survival of irradiated bacteria decreased considerably when they were cultured using a substrate unsuitable for fermentation, suggesting that respiration impairment is a key factor in cell killing. This observation is in keeping with the notion that the respiratory chain is the main target for the action of sunlight in Escherichia coli.

A strategy for structure-activity relationship study on antioxidants in Echinops latifolius Tausch extracts by online HPLC-radical scavenging detection coupled with ESI-IT-TOF-MS^(n)

Echinops latifolius Tausch(ELT)is the traditional Mongolian medicine for the treatment of osteoporosis,and the ambiguous composition of active ingredients is an important factor in restricting the modernization and globalization of this herb.Considering the traditional activity screening strategy is time-consuming and labor intensive,online HPLC active ingredient detection coupled with ESI-IT-TOF-MS^(n) strategy was employed in this study to isolate,identify and screen active compounds from the herbal medicines at the same time.The structure-activity relationship of these compounds was elucidated as well.Owing to the association of osteoporosis progression and oxidative stress,the antioxidants screening from ELT could be a good interpretive of the active substance in this herb.Meanwhile,DPPH equivalent method was an indicative of the most powerful antioxidant in ELT.Consequently,the screening and identification of the antioxidants in ELT was performed by using on-line HPLC-radical scavenging detection coupled with ESI-IT-TOF-MS^(n) strategy,and the structure-activity relationship was investigated based on DPPH equivalent method.Finally,20 constituents(including apigenin glucosides,caffeic acid,biscaffeoylquinic acids,biscaffeoylquinic acid methyl esters,ect.)were characterized in ELT extracts,and 18 components showed appreciable radical scavenging capacity.In addition,the structure-activity relationship study was carried out based on 14 compounds isolated from our laboratory,and the structural requirements of the compounds on antioxidant activity were obtained:(1)compounds with phenolic hydroxyl groups could have antioxidant activity;(2)the antioxidant activity could not be facilitated by the number of hydroxyl groups,but affected by the number of caffeoyl groups;(3)the substitution position of caffeoyl on quinic acid had a greater influence on DPPH activity;(4)methoxy groups could reduce the antioxidant activity.Collectively,this work provided the biochemical perspective to link active compounds and anti-osteoporosis action of ELT,and further explained how ELT worked in osteoporosis patients with bone loss.

Evaluation of the antioxidant property and effects in Caenorhabditis elegans of Xiangxi flavor vinegar,a Hunan local traditional vinegar

Xiangxi flavor vinegar（XV） is one of Hunan Province＇s traditional fermented vinegars.It is produced from herb,rice,and spring water with spontaneous liquid-state fermentation techniques.In this study,we investigated the antioxidant property of XV by analyzing its antioxidant compounds,its free radical scavenging property in vitro and in vivo,and its effects on antioxidant enzyme activity and apoptosis in Caenorhabditis elegans.The results showed that XV is rich in antioxidants.In particular,ligustrazine reached 6.431 μg/ml.The in vitro 2,2-diphenyl-1-picrylhydrazyl free radical（DPPH＊）,hydroxyl radical（＊OH）,and superoxide anion radical（O2^（＊-）） scavenging rates of XV were 95.85%,97.22%,and 63.33%,respectively.The reactive oxygen species（ROS） content in XV-treated C.elegans decreased significantly（P0.01） compared to the control group.Giutathione peroxidase（GSH-Px）,superoxide dismutase（SOD）,and catalase（CAT） activities were remarkably increased（P0.01） in C.elegans after XV treatment.In addition,XV could upreguiate CED-9 protein expression and downreguiate CED-3 protein expression in C.elegans.These results prove that XV is rich in antioxidants and scavenges radicals in vitro efficiently.XV inhibits apoptosis in C.elegans probably by scavenging ROS and increasing the activities of its antioxidant enzymes.